External fixation systems use pins, wires, rods or other fixation elements to stabilize and/or manipulate tissue segments, such as bone segments. These fixation elements are typically held in space relative to each other by a fixation frame. The frame is commonly made up of rings, struts, bars or other structural members. The simplest frame is usually made up of bars (sometimes referred to as rods). To hold the bars to each other and to the fixation elements, an orthopedic clamping device with two or more clamps is typically utilized. Clamps may also be employed to hold bars to rings, pins to rings, struts to rings, and other configurations.
A user typically constructs an external fixation system by placing fixation elements into tissue segments (e.g., bone segments) and assembling a frame into an approximate shape. One or more clamps is typically loosely coupled to the frame components and the fixation elements. The tissue segments are then manually adjusted into a desired or corrected anatomic arrangement or position. The frame is then locked into place by tightening the one or more clamps to fix the tissue segments in the desired or corrected anatomic arrangement.
Some orthopedic clamps are configured to create a frame with the fixation members (e.g., bars, pins, etc.) being snapped into the clamp. The clamps are constructed of two jaws, each with opposing channels the relative shape of half of the fixation member they are clamping (such as a bar or pin). The jaws are offset from the clamping axis (i.e., the axis or direction of the clamping or compression force applied to the clamps) and initially engage at a backside across the clamping axis such that the jaws pivot toward or away from each other along the clamping axis. The jaws are biased towards each other along the clamping axis by spring elements. When the bar or pin is snapped into the jaw, the spring elements hold the jaws against the fixation member. This makes assembly easy, but the spring sand the jaws often allow for the fixation member to pop out when the assembly is being adjusted into the appropriate or desired position. Some other orthopedic clamps include two jaws that slide relative to each other perpendicular to the clamping axis. The direction of opening of the jaws of such clamps is such that force applied by the fixation member against the jaw does not cause the jaw to open.
A drawback of current orthopedic clamps is that their configuration tends to allow the bars or rods to decouple from the jaws of the clamp when the assembly and tissue segments are adjusted. Another drawback of current orthopedic clamps is that because they rely on clamping surfaces or recesses of the jaws that are offset from the clamping axis, the backside of the clamps must abut to pivot the jaws closed. As clamping pressure is applied, the clamping force is thereby split or shared between the backside of the clamps and the fixation member between the jaws.
As a result, orthopedic clamps that direct all, or at least the majority, of the clamping pressure to the clamping surfaces of the jaws thereof, and thereby to a fixation member (e.g., a rod or pin) therebetween, is desirable. Further, orthopedic clamps that tend to prevent fixation members from disconnecting from the clamp when the assembly and/or tissue segments are adjusted is also desirable.